This study was conducted to investigate the possible long-term health effects, in particular carcinogenic effects, of occupational exposure to the organochlorine
insecticides dieldrin and
aldrin. We updated an earlier cohort mortality study of 570 employees involved in the production of these
insecticides. All of the employees had worked in the production plants between 1 January 1954 and 1 January 1970 and were followed for cause-specific mortality until 1 January 2001. Based on
dieldrin levels in blood samples taken during the exposure period, available for 343 workers, individual estimates of the total intake of
dieldrin were estimated for all individual subjects in the cohort. The estimated total intake ranged from 11 to 7755 mg of
dieldrin, with an average of 737 mg. One hundred and seventy-one workers had died before 1 January 2001, compared with an expected number of 226.6, giving a standardized mortality ratio (SMR) of 75.6 [95% confidence interval (CI): 64.6-87.7]. This deficit in total mortality was mainly attributable to a deficit in
cardiovascular disease mortality, but
cancer mortality was also lower than expected. The observed number of deaths from
rectal cancer was significantly higher than expected (SMR = 300.0; 95% CI: 109.5-649.3), but was most pronounced in the low-intake subgroup and appears to be unrelated to exposure to
dieldrin and
aldrin. This study reinforces the earlier findings that occupational exposure of workers to significant amounts of
dieldrin and
aldrin has not led to a higher
cancer mortality than would be found in an unexposed population.